Boris N. Yeltsin's decisive victory in the Russian Federation presidential election will propel him into a key role in shaping the future of the Soviet Union, and that outlook is now for a more rapid and radical break with the socialism of the past 73 years.

Yeltsin won 60% of the votes in the election on Wednesday, according to a provisional report by the Russian Central Election Commission, after campaigning for a popular mandate to accelerate the pace of change and broaden its scope.

His closest rival, former Soviet Prime Minister Nikolai I. Ryzhkov, who had urged a more cautious transition for the country and had the backing of the Communist Party, appeared to have won less than 20%, according to election officials. Four other candidates trailed even further behind.

In Moscow, economist Gavriil Popov won election to the newly strengthened post of mayor, and in Leningrad, law professor Anatoly A. Sobchak, another leader of the radical movement Democratic Russia, won a similar post. Both received 65% of the vote, easily defeating their Communist rivals.

Leningrad voters also endorsed, by 55%, a proposal to restore the name of their city to St. Petersburg. Although the referendum is not legally binding, the vote was emblematic of the growing popular rejection of the Communist Party and its assertion of a "socialist choice" for the country.

"Russians have seen a great event," Popov told a press conference here Thursday. "Russia has joined the family of nations and begun electing its leaders."

Acknowledging the importance of Yeltsin's election, the White House announced Thursday that President Bush will meet with the Russian leader in Washington next week.

Russians' impatience with the half-measures and temporizing of the last two years was clear as the federation's voters overwhelmingly chose for their first popularly elected president the 60-year-old Yeltsin, who had broken with Soviet President Mikhail S. Gorbachev over the pace of reform and last summer had left the party altogether. Approximately three-quarters of Russia's 105 million voters went to the polls.

"The country wants order," said Popov. "It wants concrete actions. And it expects the democratic movement to bring that order, to take those actions."

This is now Yeltsin's mission--to speak for those, now a clear majority in the Soviet Union, who want their country to be a representative democracy, to have a market economy and to adhere to the ideals of social justice.

The timing is crucial, for Gorbachev, Yeltsin and the leaders of eight other of the country's 15 constituent republics are drafting the fundamental principles that will underpin a new Union Treaty and Soviet constitution.

Yeltsin's views, once regarded as too radical even to debate, will now be the serious counterpoint to the proposals put forward by Gorbachev. He will speak not only as the president of the Russian Federation, largest of the Soviet republics, but as the only one of the 10 leaders participating in the forum, including Gorbachev, who has such an unequivocal popular mandate.

His will not be the voice of a provincial come to the capital to pay tribute or of a critic carping from the side; his will be the voice of a leader in whom the hopes and fears of perhaps two-thirds of the nation are vested.

But Yeltsin will be tested, too, by his ability to use this unmatched authority to sell the inevitable hardships that will accompany genuine reforms.

Across the vast expanse of Russia, according to provisional election returns, Yeltsin won 60%, 70% and even 80% of the votes in urban areas. While he did not do as well in smaller towns and rural areas, he still won an average of 50% of the votes there.

In very few places, and those mostly of little consequence, did Ryzhkov or Vadim V. Bakatin, an adviser to Gorbachev, who also had Communist Party support, win over Yeltsin, election officials said.

As a referendum on the Communist Party, which has ruled the Soviet Union for seven decades, on the leadership it would offer the nation in a time of turbulent change, on its vision of the 21st Century--the election was a defeat more devastating in its democracy than any "counterrevolutionary conspiracy" could ever be.

The fact that Yeltsin, as magnetic a politician as the Soviet Union has produced in decades, was an apostate, a Communist Party cadre who rose to its highest ranks, was demoted and finally quit, only dramatized that defeat.

The party's strategy had failed utterly. Realizing it had little hope of defeating Yeltsin, the party had sought to deprive him of an outright victory on the first ballot and force him into a runoff, thus diminishing his eventual victory. In the end, its candidates were rejected overwhelmingly.

This was fully the mandate, in fact, that Yeltsin and his supporters in Democratic Russia had sought in creating the new executive presidency for Russia, the country's political and economic heavyweight.

Yeltsin, who had been chairman of the Russian Parliament for the past year, has already pledged to press ahead boldly with the establishment of a market economy, based on supply and demand rather than government plans, and led by entrepreneurs, not bureaucrats.

He plans to seek control from the central government of those enterprises that operate on Russia's territory--and then begin privatizing them, selling them to investors, giving their workers and managers control, turning them over to regional and local authorities to operate.

He wants to free entrepreneurs from the myriad of government regulations that prohibit deals as anti-socialist although they promise to bring economic growth.

And he intends to push land reform, breaking up unprofitable state and collective farms and giving the land to those ready to work it as individual farmers.

Yeltsin also had a broad agenda for political reform--devolution of power, breaking the decades-old system of Soviet centralization, development of real pluralism with an end to the continuing monopoly that the Communist Party has at many levels of government and an end to party control of the military and security forces.

He has pledged to hold the first direct elections for the leadership posts of all regional, city and district councils, effectively purging Communist Party conservatives he accuses of sabotaging reform.

Nevertheless, Yeltsin chose a reform-minded Communist, Col. Alexander Rutskoy, leader of a new party group called Communists for Democracy, as his vice presidential running mate. Yeltsin said he hopes that Rutskoy will be a bridge to those in the party ready to work for radical change.

He made his peace a year ago--Gorbachev still has not--with the Baltic republics of Estonia, Latvia and Lithuania, which want to secede from the Soviet Union. He is similarly prepared to see other republics, including Georgia in the south and Moldova on the Romanian border, leave the Soviet Union when it is reconstituted through the new Union Treaty.

Yeltsin spent Thursday resting after a strenuous three-week campaign that took him to more than 20 cities. A spokeswoman said he will comment later on his victory and his plans as president of Russia.